WiMAX, or WiMAX-I, is based on the IEEE (Institute of Electrical and Electronics Engineers) 802.16e standard. WiMAX-I employs orthogonal frequency division multiple access (OFDMA) for transmissions, resulting in improved multi-path performance in non-line-of-sight environments. WiMAX-I may employ single-user (SU) or multiple-user (MU) multiple-input multiple output (MIMO) antenna techniques, adaptive modulation and coding schemes, and flexible subchannelization. A new generation of WiMAX, termed 802.16m or WiMAX-II, is currently under development.
Under 802.16m, a symbol is used for various physical layer (PHY) functionalities, such as different MIMO modes, interference mitigation, and so on. The symbol structure includes two parts: the subchannelization design and the pilot design. An OFDMA symbol is made up of sub-carriers, divided into data sub-carriers, pilot sub-carriers, and null sub-carriers (e.g., guard band). Subchannelization schemes divide the available sub-carriers into groups called sub-channels.
There exists a need for a pilot design that is optimized for the 802.16m (WiMAX-II) standard.